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AD680JR データシート(PDF) 9 Page - Analog Devices |
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AD680JR データシート(HTML) 9 Page - Analog Devices |
9 / 12 page AD680 Rev. H | Page 9 of 12 TEMPERATURE OUTPUT PIN The 8-lead package versions of the AD680 provide a tempera- ture output pin on Pin 3 of each device. The output of Pin 3 (TEMP) is a voltage that varies linearly with temperature. VTEMP at 25°C is 596 mV, and the temperature coefficient is 2 mV/°C. Figure 16 shows the output of this pin over temperature. The temperature pin has an output resistance of 12 kΩ and is capable of sinking or sourcing currents of up to 5 μA without disturbing the reference output. This enables the TEMP pin to be buffered by many inexpensive operational amplifiers that have bias currents below this value. 760 720 680 640 600 560 520 480 440 –50 –40 –30 –20 –10 0 10 20 30 40 50 60 70 80 90 TEMPERATURE ( °C) Figure 16. TEMP Pin Transfer Characteristics DIFFERENTIAL TEMPERATURE TRANSDUCER Figure 17 shows a differential temperature transducer that can be used to measure temperature changes in the environment of the AD680. This circuit operates from a 5 V supply. The temperature-dependent voltage from the TEMP pin of the AD680 is amplified by a factor of 5 to provide wider full-scale range and more current sourcing capability. An exact gain of 5 can be achieved by adjusting the trim potentiometer until the output varies by 10 mV/°C. To minimize resistance changes with temperature, use resistors with low temperature coefficients, such as metal film resistors. 6 3 2 7 4 OP90 5V + – RF 6.98k Ω 1% RB 1.69k Ω 1% RBP 100 Ω 2 3 4 AD680 TEMP GND VIN 0.1 μF 5V ΔV OUT ΔT = 10mV/°C Figure 17. Differential Temperature Transducer LOW POWER, LOW VOLTAGE REFERENCE FOR DATA CONVERTERS The AD680 has a number of features that make it ideally suited for use with ADCs and DACs. The low supply voltage required makes it possible to use the AD680 with today’s converters that run on 5 V supplies without having to add a higher supply voltage for the reference. The low quiescent current (195 μA), combined with the completeness and accuracy of the AD680, make it ideal for low power applications, such as hand-held, battery-operated meters. The AD7701 is an ADC that is well-suited for the AD680. Figure 18 shows the AD680 used as the reference for this converter. The AD7701 is a 16-bit ADC with on-chip digital filtering intended for the measurement of wide dynamic range and low frequency signals, such as those representing chemical, physical, or biological processes. It contains a charge balancing (Σ–Δ) ADC, a calibration microcontroller with on-chip static RAM, a clock oscillator, and a serial communications port. This entire circuit runs on ±5 V supplies. The power dissipation of the AD7701 is typically 25 mW and, when combined with the power dissipation of the AD680 (1 mW), the entire circuit consumes just 26 mW of power. AD680 GND 0.1 μF AD7701 CAL AGND DGND SC2 SC1 CLKOUT CLKIN SCLK SDATA CS DRDY MODE DATA READY READ (TRANSMIT) SERIAL CLOCK SERIAL DATA SLEEP 0.1 μF 10 μF 0.1 μF 0.1 μF +5V ANALOG SUPPLY RANGE SELECT CALIBRATE ANALOG INPUT ANALOG GND –5V ANALOG SUPPLY 0.1 μF 0.1 μF10μF VIN VOUT AVDD DVDD DVSS VREF AIN AVSS BP/UP Figure 18. Low Power, Low Voltage Supply Reference for the AD7701 16-Bit ADC |
同様の部品番号 - AD680JR |
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同様の説明 - AD680JR |
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